Diaphragm actuator

ABSTRACT

A diaphragm actuator having a diaphragm therein which is installed inside a cup so as to form a pressure chamber and a pressure is supplied to the pressure chamber so as to actuate the diaphragm and a rod connected to the diaphragm. The rod is supported by a bearing disposed inside the cup so that the diaphragm actuator is excellent in thermal insulation against the surrounding atmospheric temperature, thus preventing the diaphragm from being thermally deteriorated. To achieve this end, the bearing is extended to an inner peripheral surface of the cup until it touches the inner peripheral surface, and a contact surface of the bearing with the rod is formed in an arc-shaped section having the least inner diameter at its axial center.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a diaphragm actuator which correspondsto a kind of hydraulic actuator.

2. Description of the Related Art

Conventionally, there has been known a diaphragm actuator in which adiaphragm 52 is linked in an inner portion of a cup 51 so as to form apressure chamber 53, a pressure is supplied to the pressure chamber 53so as to actuate the diaphragm 52 and a rod 54 connected to thediaphragm 52 and the rod 54 is supported by a bearing 55 arranged in aninner side of the cup 51, as shown in FIG. 4. The bearing 55 is mountedto an inner peripheral surface of the cup 51 via a retainer 56, and anoutside diameter of the bearing 55 is set to be significantly smallerthan an outside diameter of the retainer 56 integrally having a springreceiving portion 56 a receiving a spring 57 for returning the diaphragm52. Further, the bearing 55 is structured such that an inside peripheralsurface is formed in a cylindrical shape and an outer peripheral surfaceis formed in a barrel shape or a circular arc cross sectional shape inwhich an outside diameter is the largest in a center in an axialdirection, so that when the rod 54 swings, the bearing 55 swings withinthe retainer 56 so as to follow the swing motion of the rod 54.

However, there are the following disadvantages in the diaphragm actuatormentioned above.

That is, since a temperature in an atmosphere in a side of the rod 54(in a vertically under side of the bracket 57 a in the drawing) riseshigh when the diaphragm actuator is attached to an internal combustionengine or the like in a vehicle via a bracket 57 a, a radiation heat isreadily transmitted to an internal space 58 of the cup 51 via the metalbracket 57 a, a lower surface portion 51 a of the cup 51 and a springreceiving portion 56 a of the retainer 56, the internal space 58 becomeshigh in temperature and the diaphragm 52 is exposed to the hightemperature. The diaphragm 52 is formed by a rubber-like elastic memberhaving a relatively poor heat resistance. Accordingly, there is a riskthat the diaphragm 52 is exposed to the high temperature and thermallydeteriorated in shorter time.

Further, in addition, the diaphragm actuator has the followingdisadvantages.

That is, at first, since the exclusive retainer 56 is provided so as tohold the bearing 55 as mentioned above, the number of parts in theactuator is large. Further, since the bearing 55 is assembled in theretainer 56 at a time of assembling the actuator and an operation ofassembling the retainer 56 in the cup 51 is required, an operation ofassembling the actuator is complex and troublesome.

Still further, since the diaphragm 52 is structured such that anoperating membrane portion 52 a and a disc-like center portion 52 b heldbetween a diaphragm retainer 59 and a spring retainer 60 are formed in auniform thickness, and is wholly formed so as to be thin. In addition,an upper end portion of the rod 54 is fixed to a laminated portioncomprising the diaphragm 52, the diaphragm retainer 59 and the springretainer 60 by means of connecting means such as a spin caulking or thelike. Accordingly, since a deformation range of a center portion 52 b ofthe diaphragm 52 is set to be small in a manner so as to suitably applya caulking load to the thin rubber-like elastic diaphragm 52, it isnecessary to severely control a magnitude of the caulking load so as tocorrespond to the caulking condition. Further, since it is a generalpractice that a pair of upper and lower washers 61 are added to thelaminated portion so as to prevent only a caulked portion in the centerportion 52 b of the diaphragm 52 from being deformed due to the caulkingload, there is a disadvantage that the number of parts in the actuatoris further increased.

SUMMARY OF THE INVENTION

The present invention is made by taking the points mentioned above intoconsideration, and an object of the present invention is to provide adiaphragm actuator which is excellent in a heat insulation against atemperature in a peripheral atmosphere, thereby preventing a diaphragmfrom being thermally deteriorated, can decrease the number of parts inan actuator and can make it easy to assemble.

In order to achieve the object mentioned above, in accordance with thepresent invention, there is provided a diaphragm actuator in which adiaphragm is linked in an inner portion of a cup so as to form apressure chamber, a pressure is supplied to the pressure chamber so asto actuate the diaphragm and a rod connected to the diaphragm and therod is supported by a bearing arranged in an inner side of the cup,wherein the bearing is extended to an inner peripheral surface of thecup so as to be brought into contact with the inner peripheral surface,and a contact surface of the bearing with respect to the rod is formedin a circular arc cross-sectional shape having the smallest insidediameter in a center in an axial direction.

In the diaphragm actuator in accordance with the present inventionhaving the structure mentioned above, since the bearing is extended tothe inner peripheral surface of the cup and is brought into contact withthe inner peripheral surface of the cup, a heat insulating layer againstthe temperature of the peripheral atmosphere is newly formed by theextended bearing. Since the bearing is made of resin and a heatconductivity of the resin is smaller than that of the metal that is amaterial of the retainer, it is possible to form a heat insulating layerwhich can achieve an excellent heat insulating effect.

Further, the bearing is also fixed to the inner side of the cup.Accordingly, the contact surface of the bearing with respect to the rodis formed in the circular arc cross-sectional shape having the smallestinside diameter in the center in the axial direction so as to supportthe rod in a swinging manner in spite of the fact that the bearing isfixed to the inner side of the cup, and in more detail, the insidediameter in the center in the axial direction is the smallest, theinside diameter is gradually expanded from the center in the axialdirection toward both end portions in the axial direction and the crosssectional shape is formed in a smoothly circular arc curved surface.

Further, since the retainer in the prior art mentioned above can beomitted from the constituting elements of the actuator, it is possibleto decrease the number of parts and improve an assembling operability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a diaphragm actuator in accordancewith an embodiment of the present invention;

FIG. 2 is an enlarged cross sectional view of the main portion of theactuator;

FIG. 3 is an enlarged cross sectional view of the main portion of theactuator; and

FIG. 4 is a cross sectional view of the main portion of an actuator inaccordance with the conventional embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Next, description will be given of an embodiment in accordance with thepresent invention with reference to the accompanying drawings.

FIG. 1 shows a cross section of a diaphragm actuator in accordance withthe embodiment. FIGS. 2 and 3 respectively show the main portion in FIG.1 in an enlarged manner.

The diaphragm actuator is employed as a waste gate actuator in aninternal combustion engine or the like in a vehicle, and is structuredin the following manner.

That is, at first, a metal cup 2 fixed to the internal combustion engineor the like is provided via a metal bracket 1, a lower cup 3 and anupper cup 4 are provided in the cup 2, and a rubber-like diaphragm 5made of an elastic material is linked between the lower cup 3 and theupper cup 4. A metal diaphragm retainer (also referred to as an upperretainer) 6 is arranged on an upper side of a center portion 5 a in thediaphragm 5 and a metal spring retainer (also referred to as a lowerretainer) 7 is arranged on a lower side thereof, whereby a three-layeredlaminated portion 8 is provided, and an upper end portion of a metal rod9 is connected and fixed to a center on a flat surface of the laminatedportion 8. Description will be given below of the laminated structureand the connection structure.

An airtight space surrounded by the diaphragm 5 and the upper cup 4 is apressure chamber 10, and a pressure port 11 is provided in the upper cup4 so as to introduce a supercharged pressure (a positive pressure) of aturbocharger (not shown) to the pressure chamber 10. The upper cup 4 isprovided with an upper surface portion 4 a formed in a disc shape in thecenter on the flat surface thereof, a taper-like inclined surfaceportion 4 b is integrally formed around the upper surface portion 4 a,and further, a flange portion 4 c for caulking and fixing an outerperipheral edge portion 5 c of the diaphragm 5 is integrally formedaround the inclined surface portion 4 b. Accordingly, the upper cup 4 isformed in a trapezoidal cross sectional shape as a whole. Further, thepressure port 11 is integrally formed in a pipe shape near an upper edgeof the inclined surface portion 4 b mentioned above toward a diametricaldirection, and all the portion between a base end portion thereof and afront endportion thereof is arranged in a flat surface layout of the cup2. Accordingly, the upper cup 4 and the lower cup 3 can be caulked andfixed all around the periphery thereof without necessity ofindependently attaching the pressure port 11 to the upper cup 4 at alater stage (even when integrally forming the pressure port 11).

A space surrounded by the diaphragm 5 and the lower cup 3 is anatmospheric pressure chamber 12 and a ventilation hole 13 is provided ina side surface portion 3 a of the lower cup 3 so as to introduce theatmospheric pressure to the atmospheric pressure chamber 12. The lowercup 3 is provided with the cylindrical side surface portion 3 a, anannular caulked portion 3 b for caulking and fixing the outer peripheraledge portion 5 c of the diaphragm 5 is integrally formed in an upperportion of the side surface portion 3 a, a lower surface portion 3 c isintegrally formed in a lower portion thereof, and an axial hole 3 d forinserting the rod 9 is provided in a center on a flat surface of thelower surface portion 3 c. A peripheral edge portion of the axial hole 3d is downwardly bent so as to position the axial hole 3 d to the holeportion la of the bracket 1. The rod 9 having an upper end portionconnected to the laminated portion 8 constituted by the diaphragm 5 andthe like is inserted to the axial hole 3 d and the hole portion 1 a, andlong extends downwards, and a link-like actuating portion (also referredto as an operating portion) 9 a is provided in the lower end portionthereof.

A resin bearing 14 for supporting the rod 9 is attached to an inside ofthe cup 2 and an inner portion of the atmospheric pressure chamber 12,the bearing 14 is extended to an inner peripheral surface 3 e of theside surface portion 3 a of the lower cup 3 outwardly in a diametricaldirection, and is brought into contact with the inner peripheral surface3 e of the side surface portion 3 a of the lower cup 3.

That is, the bearing 14 is provided with an annular or plannerdonut-shaped flat surface portion 14 a, an annular bearing portion 14 bis integrally formed in an inner peripheral side of the flat surfaceportion 14 a, and an annular press-fitting guide portion 14 c isintegrally formed in an outer peripheral side thereof. A thickness ofthe flat surface portion 14 a is about 2 mm. Since the bearing 14 ispress fitted and fixed to the inner periphery of the side surfaceportion 3 a of the lower cup 3, the inner peripheral surface of thebearing portion 14 b corresponding to the contact surface 14 e of thebearing 14 with respect to the rod 9 is formed in a circular arc crosssectional shape having the smallest inside diameter in a center in anaxial direction so that the bearing 14 can support the rod 9 in aswinging manner. A recess portion 14 d for lightening the thickness isformed on each of an upper surface and a lower surface of the bearingportion 14 b. This thickness lightening portion is formed so as to makethe thickness of the bearing portion 14 b uniform and prevent ashrinkage from being generated at a time of forming. The flat surfaceportion 14 a and the lower surface of the bearing portion 14 b areformed in so that they are aligned with each other, and are brought intoclose contact with the upper surface of the lower surface portion 3 c ofthe lower cup 3. Further, the flat surface portion 14 a commonly servesas a spring receiving portion, and a coil spring 15 for returning thediaphragm 5 is interposed between the flat surface portion 14 a formedbetween the bearing portion 14 b and the press-fitting guide portion 14c so that the upper surface is recessed, and the spring retainer 7. Thebearing 14 is integrally formed by a resin, however, it is particularlypreferable to form by a 66 nylon (containing a filler) having a smallsliding resistance, 6 nylon (containing a filler) or the like.

As shown in FIG. 3, the center portion 5 a of the diaphragm 5 is formedsuch that the only peripheral edge portion of the hole portion 5 d towhich the small diameter portion 9 b of the rod 9 is inserted is madethicker, and the diaphragm retainer 6 and the spring retainer 7 are alsoformed in a stepped shape in correspondence thereto, respectively. Thatis, the laminated structure of the diaphragm 5, the diaphragm retainer 6and the spring retainer 7 is structured in the following manner, and theconnecting structure between the laminated portion 8 and the rod 9 isstructured in the following manner.

First, the diaphragm 5 is provided with an annular or plannerdonut-shaped actuating membrane portion 5 b which elastically deformswhen actuated, a disc-like center portion 5 a held between the diaphragmretainer 6 and the spring retainer 7 is integrally formed on an innerperipheral side of the actuating membrane portion 5 b, and a holeportion 5 d to which the small diameter portion 9 b of the rod 9 isinserted is provided in a center on a flat surface of the center portion5 a. Further, a thick outer peripheral edge portion 5 c (refer toFIG. 1) caulked and fixed between the lower cup 3 and the upper cup 4 isintegrally formed on an outer peripheral side of the actuating membraneportion 5 b. The actuating membrane portion 5 b and the center portion 5a are formed so as to have a uniform thickness, however, the centerportion 5 a only is formed thick in a peripheral edge portion (alsorefer to as a rod penetrating portion) of the hole portion 5 d asmentioned above. The diaphragm 5 is formed by a rubber-like elasticmaterial, however, it is particularly preferable to form by a fluorosilicone rubber, a hydrine rubber or the like which is excellent in heatresistance.

The metal diaphragm retainer 6 is first provided with a disc-like flatsurface portion 6 a, and a hole portion 6 b to which the small diameterportion 9 b of the rod 9 is inserted is provided in a center on a flatsurface of the flat surface portion 6 a. Further, a stepped portion 6 cformed in a shape that an inner peripheral side is positioned above anouter peripheral side and in an annular shape is provided on the flatsurface portion 6 a in such a manner that it is aligned with a rodinserting portion of the diaphragm 5. A cylindrical stopper portion 6 dwhich is brought into contact with the inclined surface portion 4 b ofthe upper cup 4 so as to limit a stroke of the rod 9 is integrallyformed in the outer peripheral side of the flat surface portion 6 a soas to be directed upward.

Further, the metal spring retainer 7 is provided with a disc-like flatsurface portion 7 a, and a hole portion 7 b to which the small diameterportion 9 b of the rod 9 is inserted is provided in a center on a flatsurface of the flat surface portion 7 a. Further, a stepped portion 7 cformed in a shape that an outer peripheral side is positioned above aninner peripheral side and in an annular shape is provided on the flatsurface portion 7 a in such a manner that it is aligned with a rodinserting portion of the diaphragm 5. A cylindrical stopper portion 7 dwhich is brought into contact with the flat surface portion 14 a of thebearing 14 so as to limit a stroke of the rod 9 is integrally formed onthe outer peripheral side of the flat surface portion 7 a so as to bedirected downward.

Then, the diaphragm 5, the diaphragm retainer 6 and the spring retainer7 having the structures mentioned above are layered, whereby thelaminated portion 8 in a three-layer structure is formed, and the smalldiameter portion 9 b integrally formed in the upper end portion of therod 9 is inserted to the hole portions 5 d, 6 b and 7 b and is connectedand fixed by a spin caulking. In place of the spin caulking, the otherfastening means in accordance with a screwing or the like may beemployed.

In the diaphragm actuator having the structure mentioned above, each ofthe elements is disposed at the position shown in FIG. 1 for the initialoperation thereof, and when a supercharged pressure of the turbochargeris introduced to the pressure chamber 10 from the pressure port 11 andthe pressure within the pressure chamber 10 is over a fixed value, theassembly constituted by the diaphragm 5, the diaphragm retainer 6, thespring retainer 7 and the rod 9 strokes downward while compressing thespring 15. Further, when the pressure within the pressure chamber 10changes to below the fixed value, the assembly mentioned above isreturned upward by an elastic force of the spring 15. Accordingly, it ispossible to convert the change of the pressure into the strokedisplacement of the rod 9.

The diaphragm actuator mentioned above is characterized by achieving thefollowing operations and effects in accordance with the structurementioned above.

Accordingly, first, since the resin bearing 14 arranged within the cup 2is extended toward the inner peripheral surface 3 e of the side surfaceportion 3 a of the lower cup 3 and is brought into contact with theinner peripheral surface 3 e, the heat insulating layer against thetemperature of the peripheral atmosphere is formed by the bearing 14extended outward in the diametrical direction. A heat conductivity ofthe resin is smaller than that of the metal, thereby achieving anexcellent heat insulating effect, and a heat conductivity of, forexample, a 66 nylon is generally only 0.2 to 0.4 kcal/m·hr·° C. althougha heat conductivity of, for example, a copper is generally 1000 to 4000kcal/m·hr·° C. Accordingly, the heat of the peripheral atmosphere isshut off by the heat insulating layer and is hard to be transmitted tothe atmospheric pressure chamber 12, so that the temperature within theatmospheric pressure chamber 12 is not increased so much. Accordingly,it is possible to prevent the diaphragm 5 made of the rubber-likeelastic material from being exposed to a high heat and it is possible toprevent the diaphragm 5 from being thermally deteriorated at an earlytime.

Further, the resin bearing 14 excellent in the heat insulation is alsoexcellent in a sound insulation. Accordingly, it is also possible toreduce transmission and radiation of an operation sound.

Further, since the contact surface 14e of the bearing 14 with respect tothe rod 9 is formed in a circular arc cross sectional shape having thesmallest inside diameter in the center in the axial direction, it ispossible to smoothly swing the rod 9 in spite of the fact that thebearing 14 is fixed to the inner side of the cup 2.

Further, since the retainer in the prior art mentioned above can beomitted from the constituting elements of the actuator, it is possibleto decrease the number of the parts of the actuator, and it is alsopossible to improve an easiness for manufacturing and assembling.

Further, since the rod penetrating portion of the diaphragm 5 is formedthick and the diaphragm retainer 6 and the spring retainer 7 having thestepped shape hold the diaphragm 5 therebetween, it is possible to setlarge the deformation range of the diaphragm 5 at a time of caulking.Accordingly, it is possible to employ a wide range for controlling acaulking condition, and it is possible to improve an easiness formanufacturing and assembling. Further, since a dispersion of a magnitudein deforming in a thickness direction at a time of compressing theperipheral portion of the rod 9 and the other portions does not becomeparticularly a problem, it is possible to omit the washer in the priorart mentioned above. Accordingly, it is possible to decrease the numberof the parts of the actuator also in this view.

In this case, in the diaphragm actuator in accordance with theembodiment mentioned above, the bearing 14 is structured so as to bepressed and fixed to the lower surface portion 3 c of the lower cup 3 bythe elasticity of the spring 15 even when the bearing 14 is not pressinserted to the inner periphery of the side surface portion 3 a of thelower cup 3. Accordingly, a range of press inserting the bearing to theside surface portion 3 a of the lower cup 3 can be set to 0.

EFFECTS OF THE INVENTION AND POSSIBILITY OF UTILIZATION IN INDUSTRY

The precent invention achieves the following effects.

That is, in the diaphragm actuator in accordance with the presentinvention having the structure mentioned above, first, since the bearingarranged within the cup is extended to the inner peripheral surface ofthe cup and is brought into contact with the inner peripheral surface ofthe cup, a heat insulating layer against the temperature of theperipheral atmosphere is formed by the extended bearing. Accordingly,the heat of the peripheral atmosphere is shut by the heat insulatinglayer and is hard to be transmitted to the inner portion of the cup, sothat the internal temperature of the cup is not increased so much.Therefore, it is possible to prevent the diaphragm made of therubber-like elastic material from being exposed to the high temperatureand it is possible to previously prevent the diaphragm from beingthermally deteriorated.

Further, the bearing excellent in the heat insulation is also excellentin the sound insulation. Thus, it is possible to decrease transmissionand radiation of the operating sound.

Still further, since the contact surface of the bearing with respect tothe rod is formed in the circular arc cross sectional shape having thesmallest inside diameter in the center in the axial direction, it ispossible to smoothly swing the rod in spite of the fact that the bearingis fixed to the inner side of the cup.

Further, since the retainer in the prior art mentioned above can beomitted from the constituting elements of the actuator, it is possibleto decrease the number of parts in the actuator and it is also possibleto improve manufacturing and assembling operability thereof.

What is claimed is:
 1. A diaphragm actuator comprising: a diaphragmlinked to an inner portion of a cup so as to form a pressure chamber,pressure being supplied to said pressure chamber so as to actuate saiddiaphragm and a rod connected to said diaphragm, said rod beingsupported by a bearing extending to inner side of said cup, said bearingextending to an inner peripheral surface of said cup so as to be broughtinto contact with said inner peripheral surface and said bearing beingfixed to the inner side of said cup and a contact surface of saidbearing engaging said rod, said bearing being formed in a circular arccross sectional shape having a smallest inside diameter in a center ofsaid bearing in an axial direction, and said bearing being made of resinfor heat insulating purposes, and a spring engaging the bearing andacting directly on the bearing to bias the diaphragm away from thebearing.
 2. A diaphragm actuator as claimed in claim 1, wherein saidbearing retains said rod in a radial direction and an annularpress-fitting guide portion of said bearing is press-fitted in the innerperipheral surface of the cup at an outer peripheral side of thebearing.